The invention relates in general to boat propellers. More particularly, the present invention relates to an improved boat propeller blade edge design.
Recreational boating is an activity enjoyed by a great many people, employing a wide variety of boat types. Among the many types of recreational boats that exist are speedboats, ski boats, fishing boats, and houseboats. In fact, houseboats have become an increasingly popular form of boating as a weekend or vacation home, and for many have risen to the status of a permanent residence. For example, there are over 100,000 houseboats in the United States alone.
The common feature among these many types of watercraft, however, is that each is propelled using any one of the known types of boat drives. The known types of recreational boat drives fall mainly into two categories, jet drives and propeller drives. As the name implies, a jet drive uses a water jet generated by a thruster or an impeller, whereas the propeller drive uses a propeller powered by a suitable drive motor, as known. Jet drives are used primarily in the personal watercraft industry, and the majority of recreational boats use a propeller drive. Houseboats generally use a propeller drive provided as a part of an inboard, outboard, or inboard/outboard motor and propeller drive assembly properly sized for the boat and its handling requirements.
The problem with handling a houseboat lies largely in its size and weight. A problem that has arisen with the increasing use of houseboats is that a houseboat is slow to respond to steering and power inputs or commands, especially so when making a reverse movement in that the houseboat may not respond as quickly as needed, and more so for the novice boater than for the accomplished boater. Accordingly, and using the known types of boat propeller designs, houseboats have great difficulty achieving enough reverse thrust to be able to dock the craft in an efficient, controllable manner. This problem is particularly apparent when docking at, and moving away from fuel docks for example, where slow, careful movement is required.
There has always been an acceptable level of forward thrust using propeller drive systems with boats, but the lack of adequate reverse thrust has generally resulted in poor controllability of the boat. Over the past twenty years, as the size of the typical houseboat has increased, for example, there is a need for more or greater reverse thrust to control the boat, or to stop it in an emergency. Previous solutions to this problem centered on increasing the propeller diameter, engine size, and/or drive size.
The use of larger propellers combined with larger powerplants has resulted in some improved reverse control of houseboats. However, in so doing, houseboats and other watercraft have become environmentally unfriendly by consuming relatively large amounts of fuel while simultaneously adding increased levels of pollutants to the surrounding air and water environment within which the boat is used. Also, and under certain conditions, the people on the watercraft itself may experience an increase in the amount of exhaust fumes coming into the cabin from the greatly increased engine power requirements, and revolutions, needed to reverse the boat while also pulling the boat back through its own exhaust gases.
What is needed, therefore, but unavailable in the art, is an improved boat propeller design. In particular a propeller blade edge construction or member is needed that will improve the reverse efficiency of the propeller blade, particularly for use with larger boats, for example a houseboat.
The present invention provides an improved boat propeller comprising a hub having a plurality of blades extending outwardly therefrom, and at least one reverse thrust member connected to at least one blade of the propeller. The blade to which the reverse thrust member is connected can comprise, in one embodiment, a constant blade pitch. In another embodiment, the blade comprises an increasing blade pitch. In yet another embodiment, the blade comprises a decreasing blade pitch. A proximal edge of the reverse thrust member is formed integrally with or affixed to a leading edge of the at least one propeller blade. The reverse thrust member effectively increases the pitch of the propeller when used to propel a watercraft in a reverse direction, thereby improving the performance and efficiency of the propeller.
The reverse thrust member may be formed as an integral part of the blade or may be attached thereto. In one embodiment the reverse thrust member comprises an arcuate hook-shape defined by a radius of curvature which may be constant or may vary along a portion of the length of the reverse thrust member. In other embodiments the reverse thrust member comprises xe2x80x9cTxe2x80x9d or xe2x80x9cLxe2x80x9d shapes in cross-section.
The propeller provided may allow houseboat operation using a single engine installation, or a smaller twin engine installation for use in powering the boat as reverse drive efficiency is greatly enhanced by the invention. The invention may also have the desirable effect of reducing the amount of engine fuel consumption and pollution, and may allow engine/boat manufacturers to efficiently use a 4-stroke engine rather than a 2-stroke engine to attain the desired performance in both the forward and rearward directions. This may reduce the environmental impact of these boats.
Moreover, as houseboats do not generally exceed a speed of approximately 10 knots due to the houseboat having a full displacement hull, and as the only reason these boats are otherwise provided with massive power, i.e., larger engines, is to enable the boat to match its powerplant with the larger propeller blade designs needed to assist the boat when moving in the reverse direction, an advantage of the propeller blade design of this invention is to more efficiently direct the engine horsepower to moving the boat in the reverse direction, and with a smaller powerplant than previously thought possible in the art.
The invention may thus provide an increase of reverse thrust in the range of from 50% to 100% over the conventional boat propellers available in the art, thus tending to minimize the above-described problems of the known propeller designs.